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Chapter 14
Wildlife, Fisheries and
Endangered Species
Traditional Single-Species
Wildlife Management
•Assumptions
•Maximum Sustainable Yield: The
population size that yielded maximum
production
•Minimal Viable Population: The goal for a
threatened or endangered species
The Logistic Growth Curve
Def: The S-shaped growth curve that is generated by the
logistic growth equation
• In the logistic, a small population grows rapidly, but the
growth rate slows down, and the population eventually
reaches a constant size
Logistic Carrying Capacity:
The population size at which birth equals deaths and there
is no net change in the population
Optimum Sustainable Population:
The population level that results in an optimum sustainable
yield. The level is in some way best for the population, its
ecological community, its ecosystem or the biosphere
Classic Cases of Wildlife
Management or Mismanagement
• The American Grisly Bear
• The American Bison
• A common goal in wildlife conservation is
to “restore” the abundance of a species
• Adequate information of the abundance of a
species is very rare
Improved Approaches to Wildlife
Management
• Time Series and Historical Range of Variation
- Time Series: an estimate of a population over a
number of years
- Historical Range of Variation: the known range
of abundances of a population over some past time
interval
• Age Structure as Useful Information
• Harvests as an Estimate of Numbers
– Catch per Unit Effort: estimates previous animal
abundance. Assumes same effort by hunters.
Fisheries
• The Decline of Fish Populations
• Can Fishing Ever Be Sustainable?
– Past experience suggests that economically
beneficial sustainability is unlikely for most
wild populations
The Current Status of Endangered Species
•The Red Book
•Endangered vs. Threatened
How a Species Becomes Endangered or Extinct
Local Extinction:
Occurs when a species disappears from a part of its range
Global Extinction:
Occurs when a species cannot be found anywhere
The Good News
• Many species have been successfully
restored to an abundance
• Success is achieved when the habitat is
restored to conditions required by a species
• The conservation of wildlife offers great
rewards of long-standing and deep measure
to people